3–20

　　　　

Chapter 3: Serial Configuration Devices (EPCS1, EPCS4, EPCS16, EPCS64, and EPCS128) Data Sheet

Serial Configuration Device Memory Access

Configuration Handbook (Complete Two-Volume Set)

© December 2009

Altera Corporation

Read Bytes Operation

The read bytes operation code is b'0000 0011, with the MSB listed first. To read the

memory contents of the serial configuration device, the device is first selected by

driving nCS low. Then, the read bytes operation code is shifted in followed by a 3-byte

address (A[23..0]). Each address bit must be latched in on the rising edge of the

DCLK

. After the address is latched in, the memory contents of the specified address

are shifted out serially on the DATA pin, beginning with the MSB. For reading Raw

Programming Data files (.rpd), the content is shifted out serially beginning with the

LSB. Each data bit is shifted out on the falling edge of DCLK. The maximum DCLK

frequency during the read bytes operation is 20 MHz. Figure 3–11 shows the timing

diagram for the read bytes operation.

The first byte address can be at any location. The device automatically increments the

address to the next higher address after shifting out each byte of data. Therefore, the

device can read the whole memory with a single read bytes operation. When the

device reaches the highest address, the address counter restarts at 0x000000,

allowing the memory contents to be read out indefinitely until the read bytes

operation is terminated by driving nCS high. The device can drive nCS high any time

after data is shifted out. If the read bytes operation is shifted in while a write or erase

cycle is in progress, the operation is not executed and has no effect on the write or

erase cycle in progress.

Figure 3–11. Read Bytes Operation Timing Diagram

Notes to Figure 3–11:

(1) Address bit A[23] is a don't-care bit in EPCS64. Address bits A[23..21] are don't-care bits in EPCS16. Address bits A[23..19] are don't-

care bits in EPCS4. Address bits A[23..17] are don't-care bits in the EPCS1.

(2) For .rpd files, the read sequence shifts out the LSB of the data byte first.

nCS

DCLK

ASDI

DATA

0

1

2

3

4

5

6

7

8

9

10

28

29

30

31

32

33

34

35

36

37

38

39

Operation Code

24-Bit Address (1)

23

22

21

3

2

1

0

77

65

43

210

MSB

MSB (2)

High Impedance

DATA Out 1

DATA Out 2